The invention relates to the functional testing and quality control of injection valves, in particular for vehicle fuels.
The consumption characteristics and environmental characteristics of diesel engines can be substantially improved if the fuel is injected into the combustion chamber according to a precise time program. In particular, it is desirable to inject multiple portions of fuel in rapid succession one after the other.
In order to be able to precisely control the time program, it is desirable to know the temporal progression of the transfer function with which the injection valve (injector) converts an electrical actuation into a mass flow of fuel. In particular, the time delay between the start of the electrical actuation (electrical start of injection) and the start of the mass flow (hydraulic start of injection) is of interest.
Hydraulic pressure increase analyzers have proven particularly reliable for measurements of this type. Examples for such apparatuses are disclosed in DE 10 249 754 A1 and in DE 10 2005 056 153 A1. A testing fluid is injected under pressure by means of the characterizing injection valve into a measuring volume which is enclosed and likewise filled with testing fluid. As a consequence, the pressure in the measuring volume increases and said pressure is registered by means of a sensor. The injected mass is derived directly from the temporal pressure curve and the time derivative provides the injection rate as a mass flow. It is possible as a result of this to read in particular the start of the hydraulic injection.